Exam2_Key-2010

Exam2_Key-2010 - EXAM 2 Developmental Neurobiology, BIPN144...

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EXAM 2 Developmental Neurobiology, BIPN144 May 20, 2010 100 Points Total Question TA 1 Dileep 2 Claire 3 Jalen 4 5 20 pts. 1. In the developing grasshopper leg, pioneer Ti1 axons find their way to the CNS. a. Define the terms axon , dendrite , growth cone , lamellipodium , and filopodia . 1 pt. Axon: The single process of a neuron which carries outgoing electrical signals (action potentials) to other (postsynaptic) cells. 1 pt. Dendrite: One or more processes of a neuron which carry ingoing electrical signals (action potentials) from other (presynaptic) cells. 1 pt. Growth cone: The growing end of an axon. 1 pt. Lamellipodium: The flat spatula-like portion of the growth cone. 1 pt. Filopodia: Long finger-like projections which elongate and retract from the lamellipodium of a growth cone. b. Define the term pioneer axons . What key fact distinguishes this set of axons from others? 3 pts. Pioneer axons are the first axons to grow along a given path. 2 pts. Since these axons are the first to navigate the course, they differ from others in that they cannot follow other axon tracks. c. Define the term guide-post cells . How can one show experimentally that growing axons make contact with these cells? 3 pts. Guidepost cells are cells along the path of growing axons which are contacted by those axons to provide guidance. 2 pts. If one injects a low molecular weight dye into the guidepost cell, it is transferred to the growth cone of the axon. d. When the Tr1 neuron is ablated with a laser the Ti1 axon can still grow into the CNS, albeit less rapidly than normal, however, when the Cx1 cell is ablated Ti1 axons stall and cannot find their way. What general principle about guidance cues could explain these different results? 5 pts. Tr1 and Cx1 are both guidepost cells that help Ti1 find its path, however, other cues typically function in parallel with guidepost cells to help axons navigate. In the case of Tr1 these other guidance cues are sufficient to allow axons to find their course, although less efficiently than normal. Cx1 represents represent an exceptional case in being an absolutely required guidance cue.
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15 pts 2. Draw a diagram of a developing Drosophila eye imaginal disc indicating the following: Anterior and posterior (2 pts) ; the morphogenetic furrow (3 pts) ; the direction of furrow movement (3 pts)
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Exam2_Key-2010 - EXAM 2 Developmental Neurobiology, BIPN144...

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